Percussion fuze for rockets

ABSTRACT

A percussion fuze for rockets having an impact sensitive assembly with a spring loaded electrical contact. An explosive train has a rotor, a primer in the rotor and a detonator. A first safety inertia device has a cylindrical housing and a first spiral spring arranged in the housing. A ring abuts the first spring and a plurality of first spheres are arranged circumferentially within the ring. A second safety inertia device has a second spiral spring and a cup abutting the second spring. A plurality of second spheres are arranged circumferentially within the cup. A third safety inertia device has an electrical contact guide tube axially displaceable within the cup towards the rocket tip having an annular projection with an inclined surface. A third spiral spring acts on the contact guide tube. The guide tube is retained in the inoperative position by the second spheres arranged between the inclined surface and the inner upper surface of the housing.

United States Patent [191 De Angelis et al.

[ PERCUSSION FUZE FOR ROCKETS [75] Inventors: Giovanni De Angelis, Rome; Ettore Marchiaro, Colleferro, both of Italy [73] Assignee: SNIA VISCOSA Societa Nazionale Industria Applicazioni Viscosa Societa per Azioni, Milan, Italy [22] Filed: Jan. 19, 1972 [21] Appl. No.: 218,864

Related U.S. Application Data [62] Division of Ser. No. 2,558, Jan. 13, 1970, abandoned.

[30] Foreign Application Priority Data 51 Oct. 16,1973

Primary Examiner-Samuel W. Engle Att0rneyE. F. Wenderoth et al.

[5 7 ABSTRACT A percussion fuze for rockets having an impact sensitive assembly with a spring loaded electrical contact. An explosive train has a rotor, a primer in the rotor and a detonator. A first safety inertia device has a cylindrical housing and a first spiral spring arranged in the housing. A ring abuts the first spring and a plurality of first spheres are arranged circumferentially within the ring. A second safety inertia device has a second spiral spring and a cup abutting the second spring. A plurality of second spheres are arranged circumferentially within the cup. A third safety inertia device has an electrical contact guide tube axially displaceable within the cup towards the rocket tip having an annular projection with an inclined surface. A third spiral spring acts on the contact guide tube. The guide tube is retained in the inoperative position by the second spheres arranged between the inclined surface and the inner upper surface of the housing.

1 Claim, 5 Drawing Figures PATENTEU B8! 16 I975 sum 1 OF 4 FIG] PATENTEU 0U 16 I973 SHEET 2 UF 4 PATENTEDUBI 16 1975 3765339 saw u ur 4 BACKGROUND OF THE INVENTION In U. S. Pat. No. 3,375,786 dated Apr. 2, 1968 there is described and illustrated a mechanical percussion fuze for rockets having an impact sensitive assembly including a spring loaded striker. The explosive train includes a rotor, a primer contained in the rotor and a detonator. A first safety inertia device has a cylindrical housing with a first cylindrical spiral spring. A ring abuts the first spring and is slidably arranged on the inner wall of the housing. A plurality of first spheres are arranged circumferentially within the ring. A second safety inertia device includes a second spiral spring with a cup abutting the second spring arranged coaxially to the striker. A plurality of second spheres are arranged circumferentially within the cup. A third safety inertia device including a striker guide tube is axially displaceable within the cup towards the rocket tip through an opening provided in the cylindrical housing and a third spiral spring is provided acting on the striker guide tube. The guide tube is retained in the inoperative position by the plurality of second spheres arranged between an inclined surface of an annular projection of said guide tube and the inner upper surface of the housing.

SUMMARY OF THE INVENTION The object of the present invention is to provide substantial improvements and non-obvious modifications in the fuze as described in said Patent in order to provide a fuze capable of being operated with an electric detonator suitable to be mounted on armour piercing shells with hollow charge.

A further object is to provide extreme simplicity in construction which satisfies all safety requirements particularly handling safety and flight safety. The first safety is intended to prevent the operation of the explosive train as a result of accidental drops or impacts and the second safety to ensure the same security if an accidental impact were to incur on an obstacle situated close to the launching post.

A still further object is to provide a fuze which will operate when, upon impact of the head against the target, the electric detonator receives the electric discharge produced by a piezoelectric device or other equivalent electric means located at the tip of the projectile. A suitable resistor will dissipate the electric power possibly generated by the piezoelectric device for accidental causes, thus avoiding the possibility that when the rotor is armed the electric detonator will be suddenly under voltage and explode.

With the above and otherobjects in view which will become apparent from the detailed description below, a preferred form of the invention is shown in the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the axial section of the fuze in safety condition, i.e., prior to firing, taken on line 1-1 of FIG. 3.

FIG. 2 shows a cross section taken along the line 22 of FIG. 1;

FIG. 3 is a view similar to FIG. 1 showing the fuze during the flight-of the rocket, in the maximum acceleration stage;

FIG. 4 is a view taken along the line 44 of FIG. 3;

FIG. 5 is a view similar to FIG. 3 showing the fuze in the armed position.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, the fuze consists essentially of the parts as follows:

a. The mechanical system, which supplies the handling and flight safeties, includes the ring 3, the cup 4, the support 7, the container 2, the piston 5, the springs l3, l4, 15, the rings of balls 16 and 12 and the case 6 wherein all elements are located.

b. The rotor unit includes the rotor 31 with the electric detonator 32 provided with a sliding electrical contact 33, the abutment 34 for the rotor, the plug 35, the spring 36, the set screw 37, all located within the container 38;

c. The secondary detonator 39 threadedly mounted on the container 38;

d. The central electric contact 40, with the connecting terminal consisting of the bushing 41, the cup 42 and the screw 43, and the dissipating resistor 44. The wires 45 and 46 are connected to a piezoelectric element or other suitable electric device 50 located as desired.

Before firing the fuze is in its safety condition as shown in FIG. 1. In this condition the electric detonator 32 is turned through from the axis of the fuze and the gliding contact 33 shortcircuits the detonator through the container 38 and the priming train is materially interrupted.

The condition to allow the fuze to operate is that it should be exposed to an axial acceleration in the forward direction, that is to say from the tail towards the tip or nose. The acceleration must reach a definite magnitude (for which the fuze is preset with expedients known in the art) and it should persist moreover for a certain time.

In its operating condition, when the fuze is exposed to a forwardly direction axial acceleration of sufficient force and duration, the ring 3 overcomes the resistance of the spring 13 and is displaced rearwardly thus allowing the ring of balls 16 to move away from the axis of the fuze.

Subsequently, owing to the persisting action of the acceleration, the cup 4, acting by inertia on the spring 15, moves rearwardly since it is no longer obstructed by the balls 16 which are no longer held in place by the ring 3.

Simultaneously with these displacements, also the piston 5 slightly moves rearwards under the action of the acceleration, and releases the balls 12, which are no longer held in place by the cup 4, and which thus slide along the sloping surface of the piston 5 and the surface of the cup 4 which meanwhile has been displaced to its most rearwardly position.

At the end of all these movements, the fuze is as shown in FIG. 3. All the balls are in such condition that they cannot prevent the forward displacement of the piston which is necessary for releasing the rotor from its safety position. The rocket is now submitted to the maximum acceleration.

When the propellant of the rocket has been exhausted, the fuze is no longer subjected to acceleration toward the tip, and then the piston 5, forwardly displaced by the force of the spring 14, will move forward together with the abutment 34 of the rotor which releases the rotor 31. The rotor 31 which is no longer held, will turn under the action of the spring 36, and will stop when its abutment pin 51 bears against a suitable groove 52 provided in the plug 35. In this condition the electric detonator 32 is aligned with the secondary detonator 39 and the gliding contact 33 of the detonator is on the head of the central contact 40. The electric circuit of the fuze is predisposed to receive the electric discharge which at the moment of the impact will be generated by the piezoelectric device or equivalent means 50 located on the tip of the hollow charge head.

Simultaneously with the forward displacement of the piston, also the cup 4, the ball rings 12 and 16 and the ring 3 will forwardly displace, and at the end of said displacements, the fuze will be in the condition as shown in FIG. 5.

The fuze according to this invention will not be armed when submitted to shocks, jolts or vibrations, as provided for by the various rules known by the skilled persons in the art. The fuze will be armed, on the contrary, as disclosed, when submitted to forces of ballistic nature which are generated during the flight of the rocket carrying the fuze.

In the most unfavorable case, that is to say that of a drop in the axial direction causing the ring 3 acted upon the inertia force, to overcome the resistance of the spring 13, the duration of the motive force will always be much shorter than the time required after complete translation of the ring 3 to allow the cup 4 to be lowered, this being the condition required to arm the fuze (handling safety).

The ring 3 is carried forward by the spring 13 immediately after the impact, thus restoring the initial safety condition.

An adequate adjustment of the single elements forming the fuze may allow its use in a great many conditions observed in practice.

The present invention has been described in a preferred embodiment, but constructive modifications could be practically incorporated therein without departing from the scope of the present invention.

We claim:

1. A percussion fuze for rockets to be mounted as a base fuze on armour piercing shells provided with hollow charge comprising an impact sensitive assembly comprising a spring loaded electrical contact, an explosive train comprising a rotor, a primer contained in said rotor and a detonator; a first safety inertia device comprising a cylindrical housing having an opening, a first cylindrical spiral spring arranged in said housing, a ring abutting said first spring slidably and arranged on the inner wall of said housing, and a plurality of first spheres arranged circumferentially within said ring; a second safety inertia device comprising a second spiral spring, a cup abutting said second spring and arranged coaxially to the axis of said fuze, and a plurality of second spheres arranged circumferentially within said cup; a third safety inertia device comprising an electrical contact guide tube axially displaceable within said cup towards the rocket tip through said opening and having an annular projection with an inclined surface and an upper abutment, and a third spiral spring acting on said contact guide tube; said guide tube being retained in the inoperative position by said plurality of second spheres arranged between said inclined surface and the inner upper surface of said housing; said primer contained in said rotor being arranged perpendicularly to said electrical contact in the unarmed position of the fuze; said rotor being retained in said position of the primer by said upper abutment; and further comprising a preloaded spiral spring for rotating said rotor to bring said primer in axial alignment with said electrical contact when said rotor is disengaged from said upper abutment. 

1. A percussion fuze for rockets to be mounted as a base fuze on armour piercing shells provided with hollow charge comprising an impact sensitive assembly comprising a spring loaded electrical contact, an explosive train comprising a rotor, a primer contained in said rotor and a detonator; a first safety inertia device comprising a cylindrical housing having an opening, a first cylindrical spiral spring arranged in said housing, a ring abutting said first spring slidably and arranged on the inner wall of said housing, and a plurality of first spheres arranged circumferentially within said ring; a second safety inertia device comprising a second spiral spring, a cup abutting said second spring and arranged coaxially to the axis of said fuze, and a plurality of second spheres arranged circumferentially within said cup; a third safety inertia device comprising an electrical contact guide tube axially displaceable within said cup towards the rocket tip through said opening and having an annular projection with an inclined surface and an upper abutment, and a third spiral spring acting on said contact guide tube; said guide tube being retained in the inoperative position by said plurality of second spheres arranged between said inclined surface and the inner upper surface of said housing; said primer contained in said rotor being arranged perpendicularly to said electrical contact in the unarmed position of the fuze; said rotor being retained in said position of the primer by said upper abutment; and further comprising a preloaded spiral spring for rotating said rotor to bring said primer in axial alignment with said electrical contact when said rotor is disengaged from said upper abutment. 